Derek Chauvin is on trial for George Floyd's death

Defense expert witness Dr. David Fowler said during cross-examination that George Floyd should have received "immediate emergency attention" to reverse the cardiac arrest he was experiencing in May 2020.

Defense expert witness Dr. David Fowler said during cross-examination he agreed with the prosecution that in the majority of asphyxia deaths, autopsies will show little or no evidence of traumatic injuries, like bruising.

Prosecuting attorney Jerry Blackwell asked if Dr. Fowler agreed that in the majority of cases where somebody dies from asphyxia — or low oxygen levels — there is not necessarily any physical evidence of trauma in the autopsy.

He said that he agreed that is true "in a substantial number of the cases," adding, "I'm not sure it's absolutely a majority."

Why this is important: In earlier testimony, Fowler, a retired forensic pathologist, said it's his opinion that Derek Chauvin's knee did not impact any of George Floyd's "vital structures" of his neck.

Other witnesses who testified for the prosecution earlier in the trial said they think the prone position and the weight on Floyd's back interfered with his ability to breathe. Dr. Martin Tobin, a physician in pulmonary and critical care medicine, testified on April 8 that Floyd died from a "low level of oxygen."

At the beginning of his cross-examination, prosecuting attorney Jerry Blackwell focused in on defense expert witness Dr. David Fowler's testimony that carbon monoxide poisoning may have contributed to George Floyd's death.

Blackwell asked Fowler if it is true that he has not "seen any data, or test results, that showed Mr. Floyd had a single injury from carbon monoxide."

"Yes, true," Fowler answered. 

Blackwell then asked Fowler if he agreed that there was no finding of carbon monoxide poisoning from the Hennepin County Medical Examiner's autopsy review. He agreed.

Fowler also agreed that he did not see any data that Floyd was exposed to carbon monoxide above the levels set by the Environmental Protection Agency.

Some more context: In testimony earlier today, Dr. Fowler said that carbon monoxide from the car that Floyd was pinned down next to could have contributed to his death. "There is exposure to a vehicle exhaust, so potentially carbon monoxide poisoning or at least an effect from increased carbon monoxide in his bloodstream," Fowler said.

The Derek Chauvin trial has resumed.

Prosecuting attorney Jerry Blackwell is now cross-examining defense expert witness Dr. David Fowler, a retired forensic pathologist.

Dr. David Fowler, a retired forensic pathologist, testified that it is his opinion that the cause of Floyd's death should be "undetermined."

"I would fall back to undetermined, in this particular case," Fowler testified.

Fowler, who is the former Maryland Chief Medical Examiner, said that a death should be classified as undetermined "when you have so many conflicting different potential mechanisms of death that could lead to the manner is not clear."

Fowler, who is being paid to testify, said that there were multiple contributing factors to Floyd's death including drug use and heart disease. He also testified that Floyd suffered a "sudden cardiac event."

After defense attorney Eric Nelson was done questioning Fowler, the court took its lunch break. Before the break, Judge Peter Cahill told the attorneys that he would allow the prosecution to prepare a rebuttal to Fowler's testimony. The judge said that he would give them until tomorrow to prepare.

Remember: Hennepin County Medical Examiner Dr. Andrew Baker ruled that Floyd's death was a homicide. He said that Chauvin's restraint and compression of Floyd's neck were the primary causes of Floyd's death. Baker stood by those findings in his testimony at Chauvin's trial last week.

David Fowler, a retired forensic pathologist who is the defense's first witness of the day, said it's his opinion that Derek Chauvin's knee did not impact any of George Floyd's "vital structures" of his neck.

Here is the exchange with defense lawyer Eric Nelson:

Some context: Other witness who testified for the prosecution earlier in the trial said they think the prone position and the weight on Floyd's back interfered with his ability to breathe.

Dr. Martin Tobin, a physician in pulmonary and critical care medicine, testified on April 8 that Floyd died from a "low level of oxygen."

He outlined four factors that contributed to his low oxygen which included Floyd being in the prone position on the street, the handcuffs that were in place, Chauvin's knee on his neck and a knee on his back.

Dr. Lindsey Thomas, a forensic pathologist, said on April 9 that the "subdual, restraint and compression" of law enforcement of Floyd was "ultimately" the immediate cause of death.

David Fowler, a retired forensic pathologist, said he thinks George Floyd died due to a number of factors:

"So in my opinion, Mr. Floyd had a sudden cardiac arrhythmia or cardiac arrhythmia due to his atherosclerotic and hypertensive heart disease ... during his restraint and subdual by the police," said Fowler, former chief medical examiner at the Maryland Department of Health.

"And his significant contributory conditions would be, since I've already put the heart disease in part one, he would have the toxicology, the fentanyl and methamphetamine. There is exposure to a vehicle exhaust, so potentially carbon monoxide poisoning or at least an effect from increased carbon monoxide in his bloodstream. And paraganglioma, or the other natural disease process that he had. So, all of those combined to cause Mr. Floyd's death," Fowler said.

Some more context: Hennepin County Chief Medical Examiner Dr. Andrew Baker ruled Floyd's death last May a homicide and identified the cause as "cardiopulmonary arrest" that occurred during "law enforcement subdual, restraint, and neck compression." He stood by those findings when he testified in court last week.

Floyd had hypertensive heart disease, Baker said, "meaning his heart weighed more than it should." This meant Floyd's heart needed more oxygen than a normal heart and was "limited in its ability" to provide more oxygen when there was a demand for it.

In the middle of an altercation and being held to the ground, adrenaline would pour into the body, Baker said, making the heart beat faster.

"In my opinion, the law enforcement subdual, restraint and the neck compression was just more than Mr. Floyd could take by virtue of those heart conditions," he said.

Pulmonary critical care doctor Dr. Martin Tobin testified last week that Floyd died from a "low level of oxygen,” and that his preexisting health conditions and drug use were not relevant to his death.

Hear Dr. Fowler's testimony:  

The defense has called its next witness: Dr. David Fowler, a retired forensic pathologist.

Prior to retirement, Fowler worked at the Office of the Chief Medical Examiner for the state of Maryland.

Fowler told the court he was Maryland's Chief Medical Examiner for about 17 years.

He said he's being compensated for his time on the case at a rate of $350 per hour.

Day 13 of testimony in the trial of former Minneapolis Police officer Derek Chauvin, who has been charged in the death of George Floyd, just began.

The defense will call more witnesses today.

Chauvin, 45, has pleaded not guilty to second-degree unintentional murder, third-degree murder and second-degree manslaughter charges.

The defense's case is expected to last only a few days, and closing arguments are expected on Monday, Judge Peter Cahill said earlier this week.